three ... ago; two ... before last
Prefix used in temporal expressions to mean 'three units ago' or 'the one before the one before last'. Most commonly seen in 一昨昨日 (いっさくさくじつ, 'three days ago') and 一昨昨年 (いっさくさくねん, 'three years ago'). Not freely productive; limited to a few fixed compounds.
See also: 一昨昨日
I still remember what happened three days ago.
Looking at the statistics from three years ago, you can see the trend.
Means 'the day before yesterday' (two days ago), using a different reading for the same kanji 一昨.
two days before yesterday; three days ago
Standard kanji spelling for this prefix.
Variant using the repetition mark 々.
An extension of 一昨 by an additional 昨, marking one further step back in time.